1. Field of the Invention
The present invention relates to a fuel cell stack for generating electricity by an electrochemical reaction of a fuel and an oxidizing agent. More particularly, the present invention relates to a fuel cell stack including an improved gasket mounted in an electricity generating unit to maintain a substantially air-tight seal.
2. Description of the Related Art
A fuel cell is a device for generating electrical energy by an oxidation reaction of a fuel and a reduction reaction of an oxidizing gas. The fuel cell may be classified as a polymer electrolyte membrane fuel cell or a direct oxidation fuel cell, according to a type of fuel.
In the polymer electrolyte membrane fuel cell, a modified gas from a liquid or gas fuel and an oxidizing gas are received, and electrical energy is generated by an oxidation reaction of the modified gas and a reduction reaction of the oxidizing gas. The polymer electrolyte membrane fuel cell has excellent output performance, a low operational temperature, and quick start and response characteristics. Therefore, the polymer electrolyte membrane fuel cell is widely used as a mobile power source for vehicles, a distributed power source for buildings, and a small power source for electrical devices.
The direct oxidation fuel cell receives liquid fuel and air to generate electrical energy by an oxidation reaction of the fuel and a reduction reaction of the oxidizing gas.
The fuel cell includes an electricity generating unit that is a unit cell for generating electrical energy. The electricity generating unit includes a membrane electrode assembly (MEA), a pair of separators (with the MEA between the pair of separators), and a gasket that is provided at an edge of the MEA and allows the space between the pair of separators to be air-tight. Multiple electricity generating units are sequentially arranged to form one stack.
One of the separators includes a channel for supplying the fuel to a surface facing the MEA, and a manifold penetrating through the separator. The manifold communicates with the channel so that the fuel is provided to the channel through the manifold. However, in the fuel cell stack according to the prior art, a membrane of the MEA expands at a boundary area of the manifold and the channel, and therefore the membrane problematically blocks the channel.
Therefore, in the fuel cell stack according to the prior art, as shown in FIG. 10 to FIG. 12, a bridge 260 is additionally provided at the boundary area of the channel 241 and the manifold 244 so as to solve the problem of the membrane blocking the channel 241. That is, the bridge 260 prevents (or blocks) the membrane from expanding, and provides a path from the manifold 244 to the channel 241.
However, since the bridge 260 is additionally provided in the fuel cell stack according to the prior art, an additional cost occurs, and thickness of the separator 240 and the gasket 250 is problematically increased by the height of the bridge 260.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.